1. To meet aggression with aggression. In other words, if someone is talking shit about you, you talk shit back, or do something worse, such as beating their ass. Or say, if someone shoots up your house, you shoot up theirs, or do something worse, maybe like blowing it up. Basically, it means to get back at someone for what they did to you.

2. The opening track on Ride the Lightning, Metallica's second studio album. It is a fast-paced song, and it includes a good guitar solo, just like most Metallica songs. The song talks about revenge, and how war could end the world. A very awesome song to say the least.

1. Marshall: Bro, Ray keeps talking shit about you.
Jordan: Yeah, I know. I'm about to Fight Fire with Fire.
Marshall: And how are you gonna do that?
Jordan: By kicking his ass.

or

Marlon: Jamal, man, them boys just shot up Lisa's house!
Jamal: Dog, we gotta Fight Fire with Fire.
Marlon: Yeah, we should blow their shit up.

2. Chris: Hey, Frank, you ever hear Fight Fire with Fire by Metallica?
Frank: Hell yeah, that song is amazing!
Chris: Yeah, I know. I hear it's hard to play on a guitar.
Frank: You think? Just listen to it!